Of course it makes easier to get around if you can speak Japanese, also it makes you able to interact with deeper culture... even learning at least Arigatogozaimasu (thank you very much) makes easier to interact with local people.
However, in city sides like Tokyo, Kyoto, and Osaka has lots of signs in English. All train station shows station names and exits in English. You can get subway maps in English at stations. There maybe issues at restaurants, but many restaurants in major sightseeing spots offer English menu now.
This is my first planned trip to Japan.I'm hoping that the train network is not too difficult to navigate,especially Tokyo with so many train lines and no knowledge of the Japanese language.
No you don't.
If you can speak English, many Japanese can understand easy English words.
Communicate with written language, it makes most Japanese easier to understand than spoken language.
I think the number of international visitors has increased recently but most of them do not speak Japanese.